Lamp



Feb. 24, 1931. W. H, WOOD 1,793,661

LAMia Filed F. 26, 3.926 2. ShefS-Sheet l Feb. 24, 1931. W H, WOOD 1,793,661

LAMP

Filed Feb. 26 926 2 Sheets-Sheet 2 F; 6 William/'1T Wood Patented Feb. 24%, 93?.

WILLIAM. H. WOODLOE SOUTH'. EUCLID CHI@ LAMP Application illed February 26, 1926. Serial No. 80,785..

This invention relates to vehicle headlights and has for its objectthe provision of an improved reflector designed primarily for use with multi-filament lampA bulbs, which shall be easy to make and polish or repolish and which shall afford an improved distribution and pattern of the light produced; the provision of a refiector which shall produce a beam which changes in position in a predetermined way, with or without change of pattern as may be desired, upon use of one or another filament; the provision of a reflector which exhibits a minimum of sensitiveness to changes in the position of the light source other than 'a vertical direction. ln the fol. lowing description it should be kept in mind that my improved reflector is equally usable with a single 'filament lamp bulb and produces a light of maximum lighting efficiency with a minimum of wasted or obgectionable rays.

When automobiles first came into use the only known lights were very dim. The speed requirements soon entailed the use of brighter lights, which exhibited the defect of dazzling meeting travelers and leading to accidents. The next step was to dim the light upon meeting another vehicle but this had the disadvantage of reducing the amount of light and until the drivers eyes were able to adjust themselves to the situation he was in partial blindness at the moment of greatest need. Another attempt lay in the employment of a focussed filament for the driving light and an un-focussed filament for the passing light, (either in the same or a different bulb) but these entailed the same dificulty.

More recently it has been suggested to employ two filaments of equal candlepower so but diliiculty has been experienced in the pro-- vision of a lamp (either by the use of reflectors or lenses or both) which should do this. The specific object of my invention is to accomplish this easily, simply, cheaply and with certainty, either by the refiector alone or by the use of a reflector vassisted by a lens; 5 the accomplishment of this specific object also located as to cause merely a limited elevasatislies the general objects heretofore mentioned.

Inthe drawings laccompanying and forming a part of this application I have shown a preferred physical embodiment of my inven- 5u tion, wherein Fig. 1 is a diagram of the different portions of my improved refiector viewed from 1n front; Figs. 2, 3, and i are axial sectional views corresponding to the lines 2 2,

3--3,'and 4-4 respectively of Fig. 1; Fig. 5 6o is a vertical sectional view of a completed -reiector having a double filament lamp *bulb therein; and Fig. 6 illustrates the light pattern produced by each filament of the lamp bulb shown in Fig. 5. I 65 The lateral portions of my improved re-4 flector both above and below the central horizontal'plane are defined as a surface of revolutionA of a parabolic generator A about its own axis a-a, which becomes the main refiec'tor axis and in use is supported approximately horizontal (to be strictly accurate it is preferably used with a downward inclination of about 1, but :for most descriptive puliposes this can be considered as horizon- 7E ta As a result the horizontal axial section of the reector is defined by atrue parabola as shown in Fig. 3. The portion of the reflecpr isidentied by the little crosses -lin The top and bottom median portions are leaned downwardly as compared with such paraboloid Surface and are producedlby rotating suitable generators about axes which 35 are parallel to the axis a-a but more distant so that these portions have a longer radius of curvature than the paraboloid. vThe generators employed forl defining these top and bottom surfaces are different. That at the top is indicated at B and leaves the par abola B at some point g which must be atthe rear of the parameter p, p. This generator B diverges progressively from the parabola A with increasing distance from the vertex of the parabola A, and may itself be considered as a segment of a suitable parabola suitably inclined. For successful use with a double filament lamp the point g must be located a substantial distance rearwardly of l@ the parameter, and may even approach the l vertex. This generator is rotated about an axis b-b which is parallel to and below the axis a-a. I have had good success locating this axis b-b at the parametral circle'although this particular distance is not significant and may be either increased or decreased according to the width of the diffused light beam desired. The surface of revolution `B thus defined lies wholly inside of and beneath the paraboloid surface A (See Fig. 2) and is identified by the small circles o o in Fig. l'. This surface extends to symmetrical points on opposite sides of the vertical plane and tends to meet the paraboloid surface by curved lines indicated generally at 1, r. In practice, however, this merging is preferably effected by some transition-surfaces, identified by s, s, and tft, and one convenient way of producing such transition surfaces' is to employ generators intermediate between A and B and revolve the same about axes angularly displaced from b aroundthe parametral circle or such other distance as may be chosen. I have shown two transitional surfaces between the vertical and horizontal regions, but more or less can be employed. In fact the smoother and more nearly uniform the surfaces blend together the better is the refiector. In practice the -lines 1', 1, etc. ought not to be apparent.

The generator employed at the bottom is indicated at C and preferably conforms substantially to a parabola whose axis c, c is inclined downwardly as compared with the axis a, a. For certain practical reasons I prefer that the focal length of the parabola C be slightly less than that of the parabola A, e. g. in the proportion of 11/2 in. to l'f in. and to locate the focal point f of the parabola C -116 in. directly below the focal point f of the parabola A. This means that the vertex of C is displaced inside Vof the verteX .of A and also that C is located inside ofAuttheir (substantially) common parameter,` ,but owing tothe inclination of its axis it; leans downwardly faster than the curve A at equivalentpoints. This generator, C, is revolved'about an axis 0.', c', which is parallel to the axis a-a and above the same, in this case being located on the paramf etral circle.` As a consequence this lower median portion exhibits a. smaller transverse curvature than lthe paraboloid but tends to intersect the paraboloid surface along lines u, u located symmetrically upon opposite sides of the-vertical plane.4 The surface is identified by 'v fv, in Fig. 1,' and its margins are merged into the paraboloid surface by transitional surfaces lw, w, similar to vthose at s, t, and produced in an equivalent manner, so that the lines u u are preferably obliterated.

A sectional view on a diagonal such as 4-4 forming a. unitary reflector illustrated in Fig. 5. In orderv vto accommodate the lamp socket sleeve 'E a circularV flat spot is produced at the tip of the' punch which produces a' flat heel L which facilitates the attachment ofthe sleeve and also merges the oifset apicesY of the' surfaces A and C. This sleeve E is preferably coaxial with a-a, and the bulb G When this bulb is coaxial with the sleeve. contains two filaments M, N, located one -above the other the following features of operation are exhibited.

It is obvious that one or the other or both of the filaments must be vertically displaced from the focal point of A, and it makes little difference which condition exists incase the reflector berproperly adjusted' thereto. It is easily demonstrated that if the reflector were truly paraboloid any elevation of the light source above the focal point will tend to throw downwardly all rays reflected near the vertex and throw upwardly allrays reflected near the mouth, while those rays which are reflected at the parameter change their position not at all; but this condition exists only in and near the vertical plane. At the horizontal plane the only effect produced by raising the light source is to change very slightly the angle of incidence and the result in every case. all around the reflector, and equally behind as before the parameter, is to depress the reflected rays. this depressing is greatest at the sides of the reflector since here the angle of incidence is changed the most; at points nearest the vertical plane the elevation influences the reflected beam chiefly by parabola action; nearer the horizontal it is the angle of incidence which controls the reflected beam; and at points between the two effects merge into each other.

It should be noted also that the action differs at opposite sides of the parameter. At the rear of the parameter all portions, both vertical and lateral, tend to throw the beam The amount of downward as the source is raised, and the tal the action is decreased and at points ap` preaching the vertical the action is reversed. Also the greater is the distance in frontof the parameter the greater becomes the parabolic action as compared with thesimple reflective action.

All the description of the last two paragraphs is basedupon the behavior of a simple paraboloid and shows how a simple displacement of the light source vertically ofA the axis gives rise to a number of different actions at various parts of the reflector with a marked change in the light pattern.

By the construction-heretofore described l remove those parts of the paraboloid which normally produce the contradictory and confusing elfects last described. All portions of the reflector marked -i- -lremain in concentrating relation with the light source at all times, and any elevation or depression of the light source as by change from M to N serves merely to elevate or depress the concentrated portion H of the light beam shown in Fig. 6. The median portions of the reflector o, o and o, fv, both above and below, which normally would move oppositely to the main beam are, by the reduction of lateral curvature, spread sideways, and'by the leaning position depressed, so as to illuminate the P and Q points shown in Fig. 6. The sensitiveness of these regions to parabolic action may be overcome if desired by balancing them against each other. It will be noted that a part of o, o and a part of fv, 'u is behind the parameter as well as in front. This is adopted for `two reasons; first because it is necessary to modify the paraboloid at and immediately behind the parameter since the parabolic effect produced by elevating or depressing the light source is zero at this point whereas it was desired to cause the beam H t'o move as a Whole; the second reason, and the one which determines how far back of the@ parameter to carry these points is as follows:

The portions o, o and fv, 'v are essentially parobolic and include their parameters so that their front and rear ends exhibit4 an opposite effect upon the light beam as the light source is lowered or raised. Accordingly upon any given vertical movement of the light source the eect otone end of each of these median portions is to tend to counteract thev effect 4produced by the other end, and the total resultant effect depends upon the relative amount of light falling on'those ends. It will be remembered that the light from these regions is that which illuminates the points p and Q in Fig. 6. With the arrangement shown in those views the result of changing from M to N or vice versa is to shift the portionHofzthebeamabout 2while shifting the Qpoints about lfinthe same directon and'- this is a very desirable arrangement since it drops the intense beam out of the way when meeting other vehicles while retaining the lateral portions as a passing light, these being already too low to produce dazzle. It is easy, however, either to increase or to decrease this movement of the Q. points. Thus one way increase the movement is to increase the proportion of the median sections behind the parameter, as by moving point g nearer the vertex or by narrowin the portions in front of the parameter; whi e an opposite mode of treatment (combined if desired with a slight change in angle or character of curve) can be causedl to keep these points substantially still, only the intense beam being moved. tthus becomes possible, with a very small change in shapes or dimensions, to produce exactly the character and behavior of light beam which may be desired.

In explanation of Fig. 6 it may be stated that the location of the points and their re- -spective illumination by myvimproved reliector is as follows, the apparent candlepower being given:

Intensity with lower Point filament Location The two filaments were of equal candlepower, rated at 21 each. The central most intense beam is derived from the lateral margins, the beam denominated J from portions of the heel removed from the lateral margins,

and the portion K from the top and bottom median portions. C and D points are lighted by the Hat portion L at the heel which produces a diffused illumination additional to that shown in Fig. 6.

In case it be desired to spread the light I further laterally a vertically luted or corrugated glass may be employed, or an incandescent lamp used which has a wider V or bar shaped filament, or other known expedients employed such as latting of striating the reflector in vertical zones. It

is also within my invention to use my improved reector with the usual single tialment bulb and the resultin one or the other. of-theeams herein described or shares their characteristics according as the filament is located in the reflector. An intermediate position of the ilament is best, however, when only a single ilament is used,- since the reliector is then peculiarly insentitive to the location of the filament and it becomes safe to employ a fixed socket without adjustment provisions. v

It will be understood that a great many changes in detail and appearance can be made within the scope of my invention.

Having thus described my invention what I claim is l. In a vehicle headlight, a reflector having at each side a portion extending both above and below the horizontal plane and from the heel portion substantially to the forbeam corresponds to ward edge thereof defined by a single paraboside and extending'both above and below the loid formed about a substantially horizontal axis and having its portions at and upon each side of the vertical axial section leaned downy wardly as compared to said first named paraboloid surface at corresponding points, said last 'named portions having a transverse curvature which is less than would be produced by rotation aboutthe paraboloid axis.

2. In a vehicle headlight, a reflector having its lateral 'portions defined by a parabolic points and progressively diverging from said paraboloid surface with increasing distance from the vertex, said reflector having its low'- er median surface produced by rotating a third generator about an axis which is paral-l lel to and above suoli first axis, said third generator consisting of a parabola whose axis is inclined downwardly as regards the first named axis, said upper and lower median surfaces merging into said paraboloid surface at symmetrical points on opposite sides of the vertical plane.

3. In a vehicle headlight, a refiector having lateral portions which are Ysubstantially parabolic, and havingmedian portions both above and below the axis which are parabolic to afocal point which is located in the same vertical axial plane with the focal point of the first named paraboloid, the portions of said reflector lying in the vertical plane behind the focal plane and below the axis being 5. In a headlight, a. reflector having at each horizontal plane, a surface whose boundaries conform to a single paraboloid surface Whose axis is substantially horizontal, the portions of said reflector located 45 from the hori-v zontal plane and forward of the focal plane being located below said paraboloid surface, and the portions of said reflector located 90 `from said horizontal plane and in front of the focal. plane being leaned downwardly more than said paraboloid at equivalent points.

6. 'In a headlight a reflector having at each side and extending both above and below the horizontal plane, a portion defined by a paraboloid formed upon a substantially horizontal axis, the portions of said reflector locatedv 45 from the horizontal plane in each direction and in front of the focal plane being lo- 'cated below the surface of said paraboloid, and the portions of said reflector at and near 90 from the horizontal-plane and in front of the focal plane having a lateral curvature which is less than the lateral curvature of said paraboloid surface.

7. In a headlight, a reflector having at each side and extending both above and below the horizontal plane a portion defined b a single paraboloid, the mouth portions o said relector located 45 from the horizontal plane signature.

WILLIAM I-I. WOOD.

located in front of the surface of said first y paraboloid and those portions lying in the vertical plane and above the axis and in front of the focal plane being located below said first paraboloid surface, portions ofsaid re- Hector adjacent to the vertical axial plane having a smaller curvature in a horizontal direction than corresponds to a surface of revolution about either parabolic axis.

4. In a vehicle-headlight, in combination a refiector having itsJ two lateral portionsat and near the horizontal plane and extending to its forward edge defined substantially by segments of a single paraboloid having a substantially horizontal axis, the portions of said refiector at and near the vertical axial plane at and forward of the focalplane having a smaller. curvature in a lateral -direction and a greater downward inclination in a fore and aft direction than is exhibited by said first named paraboloid at equivalent points, and a lamp bulb having two independently usable concentrated filaments located one above the other and intersected by the same vertical line which passes through the focal point of said paraboloid. 

